With a remarkable growth of related technologies, a great variety of mobile electronic devices, e.g., smart phones, tablet PCs (Personal Computers), PMPs (Portable Multimedia Players), PDAs (Personal Digital Assistants), laptop PCs, and wearable devices such as a wrist watch or an HMD (Head Mounted Display), are increasingly popularized due to their high usability and good portability.
Such mobile electronic devices today outgrow their respective traditional fields and hence reach a mobile convergence stage by offering various functions, e.g., an SNS (Social Network Service), a wireless internet access, a multimedia service, an augmented reality information display, etc. as well as an inherent call function.